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From "Alex Petrov (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-7826) support non-frozen, nested collections
Date Thu, 07 Apr 2016 13:39:25 GMT


Alex Petrov commented on CASSANDRA-7826:

I'm doing a small research on what it may take to get this implemented. It's clear that it'll
require new syntax for nested lookups and updates, but I wanted to address some larger things.

  * {{ComplexColumnData}} is a bag of {{Cells}}, although having nested collections would
require {{ComplexColumnData}} to also contain {{ComplexColumnData}}. 
  * in most of places, such as {{Operation}}, there's a single-level mapping: retrieve a {{ColumnDefinition}},
and then build {{CellPath}} directly within this column 
  * it might be good to allow nested {{CellPath}} iteration (maybe? making {{CellPath}} multi-level,
and allowing nested access)
  * {{Insert}} and {{Update}} operations that don't require nested access (for example, {{UPDATE
%s SET c[0] = [5,6] WHERE a = 1 AND b = 2}} given {{c is list<list<int>>}} are
a much simpler, since they don't require finding a nested cell, although nested collections
are now stored as {{blobs}}, which is a main "issue" here
  * {{Operation}}s such as {{Set|DeleteField|Addition|Subtraction}} would probably require
the biggest changes, aside the mentioned {{Cell}} changes 

Please correct me if I'm wrong somewhere.

> support non-frozen, nested collections
> --------------------------------------
>                 Key: CASSANDRA-7826
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: CQL
>            Reporter: Tupshin Harper
>            Assignee: Alex Petrov
>              Labels: ponies
>             Fix For: 3.x
> The inability to nest collections is one of the bigger data modelling limitations we
have right now.

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